Inter-modal attention: ERPs to auditory targets in an inter-modal oddball task

This study investigated ERPs to auditory targets amidst visual standard stimuli in an inter-modal oddball task. Twenty subjects completed three tasks in random order: 1) an inter-modal oddball, 2) an auditory oddball, 3) and a single tone task. Target stimuli were identical in each task. In the inter-modal condition the auditory N100, N130 and P200 components were not substantially affected by the presence of the visual standard stimulus. In contrast, the later components P250, P300 and P350 differed between conditions. It is suggested that the processing of auditory targets in the inter-modal oddball occurs in two-stages--with initial auditory processing occurring independently of the visual standards, followed by activity indicative of an integration of stimulus characteristics. Furthermore, these data indicate that the context in which stimuli are presented affects the ERP. These results are discussed in light of previous findings in inter-modal research.